Yes. Actually a lot of Japanese media was. Allegedly a lot of the foundations of the Nasuverse spun out of a series of World of Darkness games Kinoko Nasu played during the 90s.
And therein is kind of a clue as to why TRPGs were so niche - the dice. Until the advent of online shipping, getting a hold of a set of polyhedral dice to play most of the games was nearly impossible in Japan (for reference, even in the 90s I could walk into most major bookstores in the US and get a set). You could find standard six-sided dice to play games like WoD or Sword World, but playing something like CoC or D&D was out of the question. Then in the 2000s, possibly encouraged in part by resurgence of interest in TRPGs in the west (with the 3rd edition of D&D and the OGL) and in part by an increasing awareness of the hobby in otaku subculture, more people started taking to it.
Fun fact: Similar to how we have tourists in the west who exclusively consume TRPG content through shows like Critical Role or The Adventure Zone, there's long been a 'Replay' culture in Japan wherein most people with awareness of the hobby consume it via transcribed game sessions with illustrations.